In recent years, mobile terminal devices have become devices that people most often come into contact with, carry, and use. Such mobile terminals are already functionally expanded beyond the function of a landline telephone, which has merely been used for a call, and are used as functional devices that provide specific functions according to a need and purpose of the user, and are also used as amusement equipment that has an important role in the leisure industry.
With this tendency, the functions of the mobile terminal are becoming more complicated and various, and the size of the mobile terminal is becoming larger. As a result, portability of the mobile terminal is gradually deteriorating. Accordingly, the use of an auxiliary terminal that allows some simple functions of the functions of the mobile terminal to be performed is increasing.
The auxiliary terminal is generally used in a form such as a wristwatch, spectacles, and a necklace. Especially, the smart watch in a form of a wrist watch is most commonly used among various forms. The smart watch is frequently exposed to the user as compared with the mobile terminal due to the characteristics thereof. Generally, the mobile terminal is stored in a pocket or a bag while moving, whereas the smart watch is used while being worn on the body, whereby the user can frequently check the smart watch. Particularly, the smart watch can be referred to as a device that the user checks most frequently among other wearable auxiliary terminals.
However, even if the auxiliary terminal has excellent design and usability, because the user frequently comes in contact therewith, he/she can become easily bored with the design of the auxiliary terminal. Also, due to the characteristics of mass-produced products, it is difficult for the user express his/her own characteristics via the watch.